Scores of textbooks attest that John Locke is the most important intellectual influence on America’s Founding. No other first-tier philosopher can provide a moral and theoretical justification for the United States, its traditional culture, and its form of government. Even the skeptics who question Locke being the only influence concede he was the most significant. The practical problem is that modern experts are confused about what Locke actually thought.

Historian Louis Harz wrote a 1950s classic finding that Locke set the framework for all of American culture and government but that it “is no easy problem” to decide what Locke meant. Cambridge’s Peter Laslett called Locke “perhaps the least consistent of the great philosophers.” George Sabine’s once-dominant political theory text claimed Locke “stands before all other writers” about America and the West, but it “was exceedingly difficult to understand exactly what Locke believed to be the philosophical justification for his theory of natural rights.” The leftist academic C.B. Macpherson explained this alleged ambiguity by saying that Locke’s explicit philosophy hid what he really was, a “possessive individualist”—and that that could not have been acknowledged, for it undermined any real social theory. The classical philosopher Leo Strauss felt compelled to exclude everything from Locke’s thought that he, Strauss, deemed not sufficiently rationalist. Even today an important modern philosopher like Edward Feser can dismiss Locke as ultimately incoherent.

As Locke is so significant, it is not surprising that many of those who find he is either difficult or confused actually disagree with him. Strauss, for, example starts with rationalism and revelation as the only two essential—and mutually exclusive—modes of thinking. One’s thoughts arise from either Athens or Jerusalem, but not both. Since Locke claimed belief in a life after death, following revelation, he cannot be a rationalist. Yet since he must be rational (how else could he be so widely respected?) there must be another, “hidden” interpretation that is rational. So in Natural Right and History (1953) Strauss boldly excludes all revelation and manufactures a Lockean “partial law of na­ture.” Its secret is that Locke did not take rev­elation seriously and really was a pure rationalist of hedonism, hid­ing his true philosophy of utilitarianism so that it could appeal to his readers, whose religion held virtue rather than pleasure as its highest goal.

Sabine similarly held in his A History of Political Theory (1937) that Locke was personally religious but this did not influence his philosophy, which was “as egoistic as that of Hobbes”—although conceding it took his “English successors” to turn Locke’s thinking into true utilitarianism. Sabine, a political liberal, comes closer to Locke’s complete position in finding that he was “an empiricist but with a large residue of philosophical rationalism and a firm belief in self-evident principles of right and wrong.” This pluralism, though, Sabine calls an “anomaly” because it is impossible to logically “unify” the different elements into an integrated rationalism.

The more conservative Feser, in his book Locke, agrees that an “appeal to God is absolutely necessary” for Locke, but that his empiricism “undercuts his argument for God’s existence.” A sound argument, according to Feser, would require Aristotelian rationalism performed in a “right order of inquiry.” Because Locke does not base his understanding on this right order of absolute rational essences, he lacks a firm basis for such belief, concludes Feser.

Treating tradition or revelation as seriously as one treated reason did not fit in mainline 20th century philosophical thinking, as Brad S. Gregory’s The Unintended Reformation(2012) makes clear. Monist rationalism, monist empiricism, or monist revelation were the categories into which thinkers were placed. But it is difficult to place Locke only with Plato or Descartes, as a rationalist, since he has also been called the founder of British empiricism—of “empirical science,” as Feser puts it. That dualism is actually why Locke is said to lack coherence. Locke holds that there are “things above reason,” that these things above reason are matters of faith and revelation, and that “an evident revelation ought to determine our assent, even against probability.” One, thus, can find rationalistic, empirical and revelational aspects in Locke’s thinking.

Locke is not alone in viewing reason as a synthesis of rationalistic, empirical, and tra­ditional elements (with the last-mentioned a combination of common sense, instinct and revelation). St. Thomas attempted an explicit synthesis of Christian revelation and philosophy. As explained by John Courtney Murray’s The Problem of God (1964), in medieval scholasticism, truth

was a many-sided edifice. . . . I should say rather that there was one universe of truth, within which different kinds of truth, and correspondingly different methodologies for their pursuit, existed in distinction and in unity. Moreover . . . there prevailed the robust belief that between the valid conclusions of ra­tional thought and the doctrines of faith no unresolved clash could or should oc­cur.

As Gregory documents, this thinking eroded in the fierce battles that later took place between Reformation and Counter-reformation theorists.

Still, there is even a modern, non-revelational defense of such synthetic thinking. In his 1965 monograph “Kinds of Rationalism,” F.A. Hayek, following Karl Popper, distinguished between a “constructive rationalism” that starts unambiguously from single essences and derives all results from them, and a “critical rationalism” that relies upon different reasoning methods—rationalism, empiricism, and even common sense and intuition—to arrive at conclusions through many means. A master axiom is not necessary or even possible, these thinkers argue, as does Gregory. In Conjectures and Refutations (1963), Popper even gives tradition the pre-eminent place in the process of understanding. Hayek specifically includes Aristotle (as opposed to Plato) and St. Thomas, as well as Locke, among the epistemological pluralists.

Strauss, of course, knew the Thomist synthesis but rejected it because it was a “dual­ism.” He rejected any attempt to use different methodologies for what he viewed as undifferentiated reality requiring a single rationality. Feser recognized that Locke was seeking a “middle way” but said it is impossible to avoid the skepticism, subjectivism, and irrationalism he sought to avoid unless it is fully accepted that a natural order “is knowable to reason” in an absolute, Aristotelian sense. Unlike Strauss’s critique, Feser’s is that Locke does not accept enough of Thomism to make his “delicate balance” successful.

There is no question Locke did move away from Aristotle and the ancients. But so did St. Thomas. The nature of the break was in Christianity itself. Feser writes that virtue and morality for the Thomist “need not be determined by an appeal to God’s commands” but is solely rational. Yet, he was careful to qualify that “the Thomistic conception [is] largely (though not wholly) secular.” That “not wholly” is critical indeed. In fact, the very structure of Thomas’ Summa Theologica (he did not call it a Summa Philosophica) routinely adds a Christian revelation to Aristotle to complete the explanation.

Pure Aristotelianism has been a difficult sell ever since its physics fell to Newtonian mechanics but, even more importantly, the absoluteness of mechanics today has fallen to probability. As philosopher Richard Rudner argued, it appears that “an adequate reconstruction of the procedures of science would show that every scientific inference is properly construable as a statistical inference.” As Feser recognizes, probability is in fact essential to Locke. Feser is concerned about Locke’s undermining of essentialism by excluding “substantial forms, substance, essence, identity and so forth” from “knowledge in the strict sense.” Yet, even he concedes that Locke accepts forms in a less strict sense and, more important, that Aristotle’s idea of forms is more material than Plato’s and, most important of all, that for Thomists knowledge “is always going to be limited in various significant ways,” which was Locke’s point.

“There is a difference between knowing an absolute and knowing an absolute absolutely,” as Richard Weaver put it. Adds Weaver: “It is even more certain there is a difference between knowing an absolute and applying an absolute absolutely.”

Four decades ago, I argued that one could not understand Locke unless he viewed him as a Christian even in the face of most existing scholarship. Part of the problem was that many merely read his Essay on Human Understanding or the Second Treatise. In Some Thoughts Concerning Reading and Study for a Gentleman (1689), Locke says that “to give a man a full knowledge of true morality I shall send him to no other book but the New Testament.” Likewise in Reasonableness of Chris­tianity and Some Thoughts Concerning Education, he wrote that Jesus was Messiah and Savior, that this was the cen­ter of reasonable religion, and that men were expected to believe this in some sense if they were to be saved for the happiness of life after death in heaven.

Locke was orthodox enough to write a discourse defending miracles and in his last years translated and extensively commented upon the Epistles of St. Paul. Even in the EssayLocke held that the “mere proba­bility” of an afterlife should move reason­able men to follow God’s law so that they could enjoy the “infinite eternal joys of heaven” rather than try “to satisfy the suc­cessive uneasiness of our desires pursuing trifles” on earth.

In making a distinction between rationalism and revelation and holding these to be different, but complementary, methods toward the truth, Locke is follow­ing Western thought.

As Paul Sigmond has noted, it has become impossible in 21st century scholarship to ignore that revelation is a serious part of Locke’s philosophical thinking. Oxford’s Jeremy Waldron broke the barrier in academic circles in 2002 with his God, Locke and Equalitydoubting “whether one can even make sense of a position like Locke’s . . . apart from the specifically biblical and Christian teaching that he associated with it.” Indeed, he argued that, without Locke’s theological justification, there is no modern liberal justification for its basic premise of moral equality between individual human beings. Just last year, Steven Forde in his Locke, Science, and Politics, argued that with probability so dominant in science today, a purely natural law cannot bear the weight of morality and that only Locke’s introduction of a law imposed from outside of nature by a Creator could.

In making a distinction between rationalism and revelation and holding these to be different, but complementary, methods toward the truth, Locke is follow­ing Western thought. To Locke (as in Thomism generally) both reason and tradition are needed. It is not a choice between opposites but a harmony. Where Locke and Thomas differ most is, once again, on this matter of probability. This was the methodology that Locke made part of his synthesis that is arguably reconcilable with the rest. Natural law has long been a central concept but it is questionable how it can fare unsupported in a probabilistic world. As Waldron and Forde show, Locke needed something outside of nature to support it. His syn­thesis may be completely invalid; faulty in this or that respect; or even just not modern. In any case the failure—if it be such—of the synthesis is not unique to Locke.

If this is a problem for him, it is likewise a problem for all of Western civilization. In the Declaration of Independence, rights are from a Creator, from “nature and nature’s God,” from both. The essence of that civilization is its tension between rationalism, empiricism, and tradition—and the need, therefore, for a synthesis. In Strauss’s time, rationalism was king and it was easy to dismiss tradition. Yet, as rationalism has peeled away successive layers of reason over the years, it has become apparent that more is needed. When even a positivist professor like Jeremy Waldron can say “I actually don’t think it is clear we—now—can shape and defend an adequate conception of basic human equality apart from some religious foundation,” it seems prudent to take another look at Locke. Not partially—all of him.

Donald Devine is senior scholar at the Fund for American Studies, the author of America’s Way Back: Reconciling Freedom, Tradition and Constitution, and was Ronald Reagan’s director of the U.S. Office of Personnel Management during his first term.